The present invention relates to a polar transmitter and related signal transmitting method, and more particularly to a polar transmitter which delays an in-phase signal and a quadrature signal before input into a Coordinate Rotation Digital Computer to make a converted amplitude component synchronizes with a converted phase component, and a method thereof.
A polar transmitter offers some advantages, such as a potential for reducing complexity and current consumption in the modulator path as well as eliminating the problem of image rejection, thus the polar transmitter is more suitable for implementation in advanced complementary metal oxide semiconductor (CMOS) processing technologies. More specifically, the polar transmitter is a transmitting device that converts a complex signal represented by amplitude information and phase information rather than an in-phase component and a quadrature component into a transmitting signal. In the polar transmitter, the amplitude information and the phase information are first generated from a baseband input signal generated by a baseband circuit. Next, the amplitude information is modulated into an up-converted amplitude component, and the phase information is modulated into an up-converted phase component. Then, the up-converted amplitude component and the up-converted phase component are mixed up, such as by a mixer, to generate the transmitting signal. However, the delay time caused by the amplitude modulating path may different from the delay time caused by the phase modulating path since the two paths are operated differently. If this happens, the timing of the up-converted amplitude component arriving at the mixer may deviate from the timing of the up-converted phase component arriving at the mixer. Accordingly, an inaccurate transmitting signal may by generated by the mixer. Therefore, how to synchronize the timings between the up-converted amplitude component and the up-converted phase component is a significant concern in the field of polar transmitter.